Background: The aim of the current study was to identify functional predictors of perceived impact of childhood disability among families of children with neurodevelopmental disorders and disabilities. We first examined the relationship between sub-domains of adaptive and problematic behaviour and perceived family impact. Second, we examined whether the same sub-domains would emerge as significant after controlling for the impact of child diagnosis, including autism spectrum disorder, cerebral palsy and intellectual disability. Method: Caregivers of 216 children and adolescents (M = 8.17 years) with neurodevelopmental disorder and disability completed measures of children's practical, conceptual and social skills (i.e. adaptive behaviour), behaviour problems and positive and negative family impact. Results: Indices of child adaptive and problematic behaviour were only significantly associated with perceived negative family impact. Children's practical and social skills, as well as emotional symptoms, emerged as significant predictors of perceived negative family impact, with emotional symptoms accounting for greatest variance. Including diagnosis in our statistical models did not explain additional variance above and beyond these particular sub-domains of child functioning. Conclusions: The study findings suggest that it is not children's most impaired domains of functioning that are perceived as significantly impactful by the family. The findings highlight the importance of devoting consideration to the ways in which the functional limitations experienced by children with chronic developmental health conditions similarly impact family life and well-being, regardless of disorder designation.